Basic commands
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man man // Manual pages for man command
ls // List files
cat /etc/passwd // Show content of /etc/passwd
pico newfile // Create newfile
pwd // Print working directory
mc // Midnight Commander
which nmap // Locate nmap
cd .. // Change directory
mkdir test // Create folder test
cp source dest // Copy source to dest
sync // Finish writing operations
rm file // Deletes file
rm -rf / // Recursively delete each file on file hierarchy - DO NOT TRY THIS COMMAND!

Advanced commands
-------------------------------
sudo mount /dev/sdb1 /media/mortens/AC86-9A55 // Mount sdb1 device into folder AC86-9A55
umount /media/mortens/AC86-9A55 // Detach file system from file hierarchy
file fname // Determine fname file type
ps aux // Get running applications
kill -9 `ps aux | grep vlc | awk '{ print $2 }'` // Kill vlc applications
xrandr -s 0 // Change screen size
xset s off -dpms // Disable sceen saver
useradd tester // Add user to system
dpkg -i package.deb // Install deb file
reboot // Restart machine
chmod +x steam // Add executable right to steam
dmesg // Display all messages from the kernel ring buffer
watch -c -n1 'dmesg | tail -n 20' // Watch system messages live
sudo modprobe -r uvcvideo // Turn off webcamera
sudo modprobe uvcvideo // Turn on webcamera
ftp 192.168.0.1 // Create FTP connection
telnet 192.168.0.1 // Create Telnet connection

Installation commands
---------------------
apt-get update // Update updater packages
apt-get upgrade // Update system
dpkg -i opera-stable_44.0.2510.1449_amd64.deb // Install a deb file

Install a service
-----------------
systemctl stop smbd // Stop running service
wget https://www.samba.org/samba/ftp/samba-latest.tar.gz // Download the package
tar xzf samba-latest.tar.gz // Extract it
cd samba-4.6.4 // Go into the extracted folder
./configure // Build service from sources
make // Start compilation
make install // Install the compiled application
systemctl restart smbd // Restart service

Other commands
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grep -rnw '.' -e "ToAsciiReturnCode" // Search for ToAsciiReturnCode in files in the actual folder
unzip -p document.docx word/document.xml | sed -e 's/<\/w:p>/\n/g; s/<[^>]\{1,\}>//g; s/[^[:print:]\n]\{1,\}//g' // Print content of a docx file
find / -name .cap 2> /dev/null // Search for files with redirected error output
openssl enc -aes-256-cbc -k password -in hello -out hello.enc // Encrypt file with "password"
openssl enc -d -aes-256-cbc -k password -in hello.enc -out hello.dec // Decrypt file with "password"

Penetration test commands
----------------------------------------
sudo -i // Superuser do
ssh cisco@example.com // Connect to router
service network-manager stop; ifconfig wlan0 down; macchanger -m 12:34:56:78:90:AB wlan0;  // Change MAC address
iw list // Check if WLAN network card supports monitor mode
ifconfig // Check network interfaces
airmon-ng start wlan0 // Start monitor mode on WLAN device
airodump-ng wlan0mon // Monitor mode
airodump-ng wlan0mon --bssid 12:34:56:78:90:AB -c 1 -w filename_prefix // Save packets from a specific MAC address and channel into file
wash -i wlan0mon // Provide information from access points
reaver -i wlan0mon --bssid 12:34:56:78:90:AB // Try to get WPA / WPA2 password of AP
nmap -Pn 192.168.0.1 // Get running services